The present invention relates to data processing systems in general and is concerned more particularly with a method for storing and retrieving data in such systems.
A wide variety of memory or storage devices are employed with data processing systems, and each memory device has its own advantages and disadvantages. Factors such as storage capacity, access time, volatility, cost and compatability with a particular machine or function determine whether one device or another is used. Currently disc memories are used for systems requiring a moderate amount of permanent memory capacity because they are reliable, relatively simple mechanical devices and inexpensive. One type of disc that has received wide acceptance is the floppy disc because of its rugged durability and relatively low cost. The floppy disc also operates in low cost drive units; however, the performance of such systems is compromised and in random access systems, access times can be relatively long.
The access time as stated above is one of the critical considerations in determining whether a particular memory device is suitable for given purpose. For example, in an automated artwork generation system having a work station at which a person operates with a video display to create graphic designs, access times for retrieving data shown in the display would be unacceptable if a data point could only be extracted from a floppy disc by scanning the complete disc for the selected data. On the other hand, if the access times could be reduced to periods of one second or less, the disc system would adequately serve the purpose of a memory device in the artwork generation system.
It is accordingly a general object of the present invention to provide method for obtaining direct access to data within a memory device that moves a storage medium relative to a memory head. It is a further object of the invention to provide in an automated artwork generation system a low cost data storage and retrieval method that is particularly suited to the system and does not require extended access times for storing or retrieving data.